Bushfire and ice
View Sequence overviewStudents will:
- identify that mass is lost during the combustion of a candle.
- identify that carbon dioxide and water are produced during the combustion of a candle.
- identify that oxygen is required for a combustion reaction.
- use argumentation (claim, evidence, reason) in discussing their findings.
Students will represent their understanding as they:
- identify reactants and products in a combustion reaction .
- draw a fire triangle.
- identify assumptions and limits to the validity of a method.
- conduct classroom discussion and argumentation processes.
In this lesson, assessment is formative.
Feedback might focus on:
- students’ identification of the reactants and products in a chemical reaction.
- students’ ability to generate a word equation for combustion.
- students’ identification of assumptions of the gases that are used/produced in the combustion reaction. Can they determine the impact these assumptions could have on the ability to generate a word equation for combustion?
- students’ ability to analyse methods and conclusions to identify facts or premises that are taken for granted to be true (i.e. oxygen is needed for combustion) and evaluate the reasonableness of those assumptions.
- students’ explanation of the validity of the activities used to identify the products and reactants of a combustion reaction.
Potential summative task
Students working at the achievement standard should:
- explain how scientific knowledge is validated and refined, including the role of publication and peer review.
- identify the reactants and products in a chemical reaction.
- compare information provided by the activities to generate a word equation for combustion.
- analyse and connect data and information to identify and explain patterns, trends, relationships, and anomalies.
- analyse the impact of assumptions and sources of error in methods and evaluate the validity of conclusions and claims.
- construct logical arguments based on evidence to support conclusions and evaluate claims.
- select and use content, language, and text features effectively to achieve their purpose when communicating their ideas, findings, and arguments to specific audiences.
Refer to the Australian Curriculum content links on the Our design decisions tab for further information.
Whole class
Bushfire and ice Resource PowerPoint
Sticky notes
Access to the internet and YouTube for videos on bushfires
Straw (for demonstration)
Lime water (for demonstration), prepared according to the Lab tech notes in Preparing for this sequence
Optional: Flaming flour demonstration requires funnel, plastic tubing, Bunsen burner, matches, plain flour, safety glasses
High Tech option: Carbon dioxide sensor
Each group
The following activities should be set up around the room so that students will visit each area to identify the key aspects of a combustion reaction. Provide the information for each activity (included in the Combustion reactions Resource sheet) at each station.
Activity 1
Tealight candle
Matches
Scales
Stopwatch
Activity 2
Gloves
Tealight candle
Small weight or stand for the candle
Matches
Petri dish
10-15 mL lime water
Glass jar that fits over candle
Optional: carbon dioxide meter
Activity 3
Tealight candle
Matches
Petri dish
Glass jar that fits over candle
Scales
Each student
Individual science notebook
Safety glasses, lab coat and hair ties
Combustion reactions Resource sheet
Lesson
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkRe-orient
Revisit the main causes of bushfires and their prevalence in the local area, focusing on:
- The main individual cause is lightning.
- People cause fires through arson, accidents and hazard reduction burns.
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkIdentifying and constructing questions is the creative driver of the inquiry process. It allows students to explore what they know and how they know it. During the Inquire phase of the LIA Framework, the Question routine allows for past activities to be reviewed and to set the scene for the investigation that students will undertake. The use of effective questioning techniques can influence students’ view and interpretation of upcoming content, open them to exploration and link to their current interests and science capital.
When designing a teaching sequence, it is important to spend some time considering the mindset of students at the start of each Inquire phase. What do you want students to be thinking about, what do they already know and what is the best way for them to approach the task? What might tap into their curiosity?
Read more about using the LIA FrameworkFlaming fire
Watch the video/s Fire and flame 05 – Burning flour (1:36) and/or 073 Flaming Flour2 (4:49).
Alternatively, demonstrate the phenomena in the classroom:
- Wear safety glasses.
- Light a Bunsen burner.
- Connect a funnel to one end of plastic tubing.
- Place a small amount of flour in the funnel.
- Place the funnel below and to the side of the flame (pointing away from you and the students).
- Gently blow into the other end of the tubing, so that a fine mist of flour travels into the flame (away from you and the students).
SAFETY NOTE: If completing your own demonstration, consider the location of heat or smoke detectors, and the position of students or colleagues. Consider using a Perspex barrier between the flame and students for the demonstration.
Pose the question: Is it the heat or the flame that makes the flour catch alight?
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkThe Investigate routine provides students with an opportunity to explore the key ideas of science, to plan and conduct an investigation, and to gather and record data. The investigations are designed to systematically develop content knowledge and skills through increasingly complex processes of structured inquiry, guided inquiry and open inquiry approaches. Students are encouraged to process data to identify trends and patterns and link them to the real-world context of the teaching sequence.
When designing a teaching sequence, consider the diagnostic assessment (Launch phase) that identified the alternative conceptions that students held. Are there activities that challenge these ideas and provide openings for discussion? What content knowledge and skills do students need to be able to complete the final (Act phase) task? How could you systematically build these through the investigation routines? Are there opportunities to build students’ understanding and skills in the science inquiry processes through the successive investigations?
Read more about using the LIA FrameworkCombustion reactions
(Slide 19) Encourage students to make a claim about the cause of the fire—is it the flame or the heat? Ask students for evidence of their claim, and reasoning that links the evidence to the claim. Alternatively, ask students what evidence they would need and how they could test their claim.
- What evidence/observation do you have to support your claim?
- Would the flour catch fire if you did this over a radiant heater?
- Yes, if hot enough.
- What would happen if a match was dropped into a container full of settled flour?
- The flame would go out. Flour Fireball (1:39) is an example video demonstration.
Discuss how a fire needs a fuel, a heat source and oxygen.
- Describe what happened in the demonstration.
- Was this a chemical or physical reaction? How do we know?
- This was a chemical reaction: light and heat were given off.
- Why did the flour catch alight?
- It is a fuel.
- Why doesn’t the flour catch alight when it is sitting in the container?
- No heat. And small particles of flour have a greater surface area for oxygen to react when near a heat source.
- Would the flour catch alight if it was in a lump sitting in a spoon? Why or why not?
- It would be harder for the flour to catch alight as it is more difficult for oxygen to reach the individual particles of flour.
(Slide 20) Introduce standard word equation format.
✎ STUDENT NOTES: Record the general equation: $\require{mhchem}\ce{Reactant + reactant -> product + product}$
(Slide 21) Identify one of the reactants as ‘Fuel’ (such as the flour dust).
Explain that students are going to identify the remaining parts of a combustion reaction.
Provide students with the Combustion reactions Resource sheet. Divide students into groups and introduce the following three activities.
The activities should be set up around the room, with information for each activity at each station. All students should be wearing safety glasses.
To prepare students for Activity 2, demonstrate how lime water becomes cloudy when carbon dioxide is bubbled through it by gently blowing through it with a straw.
SAFETY NOTE: Take care doing this so that you do not inhale the lime water and wear safety glasses to avoid splashing it in your eyes. If contact is made with your skin, wash the area with water.
Activity 1: Burning candle
Question: Does the candle change weight when it is burnt for 2 minutes?
Observation: Mass is lost when a candle is burnt.
Infers: Gas is produced during a combustion reaction.
- What does the conservation of mass tell us about chemical reactions?
- Mass is not gained or lost in a reaction.
- If the candle lost mass, where does it go?
- Becomes a gas.
- Do you think the gas is the candle wax or something new?
- Unable to tell. Need Activity 2 and 3.
Activity 2: Testing for a gas
Question: What is produced during a combustion reaction?
Observation: Lime water becomes cloudy.
Infers: Carbon dioxide is produced during combustion.
HIGH TECH option: Use a carbon dioxide meter to measure the carbon dioxide levels in the glass jar.
- What happened to the candle when the glass jar was put over the top?
- The flame went out.
- Why do you think this happened? What claim can you make?
- That air is needed for the candle to burn/combust. Cannot assume that it is oxygen in this activity.
- Can we tell what it is in the air that is needed for combustion?
- No.
- What types of elemental gases are found in air?
- Oxygen, nitrogen, carbon dioxide, hydrogen are the main gases.
- How did the lime water change during the activity?
- It became cloudy.
- What causes the lime water to change/become cloudy?
- Carbon dioxide.
- What claim can you make as a result of this change in the lime water?
- Carbon dioxide is produced during combustion.
- What evidence supports your claim?
- Can you provide reasoning to link the evidence and the claim?
Activity 3: Candle in a jar
Question: What is lost or produced during a combustion reaction?
Observation: Weight does not change when the glass jar is put over the flame.
Infers: Gas is lost during a combustion reaction.
Observation: The flame goes out without a fresh supply of air.
Infers: Combustion reactions need something present in the air.
- What happened to the candle when the glass jar was put over the top?
- The flame went out.
- Why do you think this happened? What claim can you make?
- That air/oxygen is needed for the candle to burn/combust.
- Can we tell what gas in air is needed for the combustion reaction?
- No.
- What types of elemental gases are found in air?
- Oxygen, nitrogen, carbon dioxide, hydrogen are the main gases.
- How did the weight change (or not change) in this activity?
- No change.
- How is this activity different to Activity 1?
- The jar trapped the gas produced.
- What claim can you make as a result of the lack of weight change?
- Gas is produced during combustion.
Combustion science
Combustion reactions do not always produce carbon dioxide.
A combustion reaction occurs when a fuel reacts with oxygen gas releasing energy in the form of heat and light. The most common general equation for a combustion reaction is
$$\require{mhchem}\ce{ Fuel (hydrocarbon) + Oxygen -> Carbon\,dioxide + Water}$$
In these examples, the mass of the fuel decreases as the water and carbon dioxide are released as gases.
This is not the only form of combustion. When hydrogen burns in the presence of oxygen, only water is produced (no carbon dioxide).
$$\ce{2H2 + O2 -> 2H2O}$$
When a metal combusts in the presence of oxygen, a metal oxide is produced.
$$\ce{Metal + Oxygen -> Metal\,oxide}$$
A combustion reaction occurs when a fuel reacts with oxygen gas releasing energy in the form of heat and light. The most common general equation for a combustion reaction is
$$\require{mhchem}\ce{ Fuel (hydrocarbon) + Oxygen -> Carbon\,dioxide + Water}$$
In these examples, the mass of the fuel decreases as the water and carbon dioxide are released as gases.
This is not the only form of combustion. When hydrogen burns in the presence of oxygen, only water is produced (no carbon dioxide).
$$\ce{2H2 + O2 -> 2H2O}$$
When a metal combusts in the presence of oxygen, a metal oxide is produced.
$$\ce{Metal + Oxygen -> Metal\,oxide}$$
The Inquire phase allows students to cycle progressively and with increasing complexity through the key science ideas related to the core concepts. Each Inquire cycle is divided into three teaching and learning routines that allow students to systematically build their knowledge and skills in science and incorporate this into their current understanding of the world.
When designing a teaching sequence, it is important to consider the knowledge and skills that students will need in the final Act phase. Consider what the students already know and identify the steps that need to be taken to reach the level required. How could you facilitate students’ understanding at each step? What investigations could be designed to build the skills at each step?
Read more about using the LIA FrameworkFollowing an investigation, the Integrate routine provides time and space for data to be evaluated and insights to be synthesized. It reveals new insights, consolidates and refines representations, generalises context and broadens students’ perspectives. It allows student thinking to become visible and opens formative feedback opportunities. It may also lead to further questions being asked, allowing the Inquire phase to start again.
When designing a teaching sequence, consider the diagnostic assessment that was undertaken during the Launch phase. Consider if alternative conceptions could be used as a jumping off point to discussions. How could students represent their learning in a way that would support formative feedback opportunities? Could small summative assessment occur at different stages in the teaching sequence?
Read more about using the LIA FrameworkFire triangles
(Slide 22) Discuss the importance of scientists collaborating to bring together different ideas and claims so that they develop a big picture of what is happening in chemical reactions.
Ask students to:
- write all their claims and observations/evidence on sticky notes (one note for each claim and evidence).
- group their claim/reasoning/evidence notes into ‘Reactant related’ and ‘Product related’ groups.
(Slide 23) Discuss the importance of not making assumptions when making observations and ensuring that you have evidence to support any claims that are being made.
- What can we tell from each activity and what can we not tell from the activity?
- What is an assumption?
- What assumptions would it be easy to make with one of these activities?
- What makes an experiment valid?
- An experiment is valid if it measures what was intended and is repeatable. It is not valid if inaccurate assumptions are made, or the experiment gives varying results.
- What key things are needed to start a combustion reaction?
- Identify fuel, oxygen and heat as the fire triangle.
- What types of substances could be a fuel?
Discuss the three elements that are required for a combustion reaction: heat, fuel, oxygen.
✎ STUDENT NOTES: Draw your own version of a fire triangle. (Slide 24)
Discuss how students’ observations can identify the reactants and products of a combustion reaction.
- Where do you put ‘heat’ on the reactant/product equation?
- Heat is not a reactant. It is energy (not matter or a separate entity).
- What are the products of combustion?
- Claim: carbon dioxide -> Evidence: Lime water showed evidence of carbon dioxide being produced.
- Claim: water -> Evidence: liquid on the inside of jar. (How do we know it is water? What test could we do?)
- What are the reactants of a combustion reaction?
- Claim: Fuel -> Evidence: Flour, matches and candle wax needed to burn.
- Claim: Oxygen -> Evidence: This cannot be confirmed in these experiments, but the work of other scientists has identified that oxygen is needed for combustion to occur.
(Slide 25) Provide students with the completed word equation for the combustion reaction.
✎ STUDENT NOTES: $\require{mhchem}\ce{(with\,heat)\,Fuel + Oxygen -> Carbon\,dioxide + Water}$
Optional: Discuss how oxygen by itself does not burn. A fuel is needed. See Fire and flame 12 – Oxygen balloon (0:59) for an example video demonstration.
Discuss what types of things act as fuel in a bushfire. Encourage students to share their ideas.
✎ STUDENT NOTES: Record your ideas about bushfire fuel.
Optional: Watch the video Fuel and fuel types (1:09).
Reflect on the lesson
You might:
- discuss the answer to the question: ‘Can combustion occur in space?’ (Slide 26). Claims 1 and 2 are correct.
- watch the video Why fires burn (2:03) as a summary.
- select one of the videos from the Fire and Flame - Peter Wothers Lecture playlist to identify some of the ways to increase or decrease a combustion reaction.
- re-examine the intended learning goals for the lesson and consider how they were achieved.
- discuss how students were thinking and working like scientists during the lesson focusing on the process of argumentation.
Assumptions and validity
All science involves making assumptions.
All science involves making assumptions (things that are true without any evidence). Prior knowledge, such as ‘fire needs oxygen’, can lead to expectations that can be tested. Students need to learn to identify the limitations of their observations or their experiments. If too many assumptions are made, an experiment will no longer be considered valid (the extent to which a test measures what was intended). The reliability of an experiment is one measure of the validity of an experiment.
The activities in this lesson are deliberately designed to provide a limited amount of information so that students are encouraged to consider the assumptions that are made and the limits of the validity.
All science involves making assumptions (things that are true without any evidence). Prior knowledge, such as ‘fire needs oxygen’, can lead to expectations that can be tested. Students need to learn to identify the limitations of their observations or their experiments. If too many assumptions are made, an experiment will no longer be considered valid (the extent to which a test measures what was intended). The reliability of an experiment is one measure of the validity of an experiment.
The activities in this lesson are deliberately designed to provide a limited amount of information so that students are encouraged to consider the assumptions that are made and the limits of the validity.